<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>文件</title>
</head>
<body>
    <h1 class="one" id="a">12312</h1>
    <form action=""></form>
    <form action=""></form>
    <form action=""></form>
    <img src="" alt="">
    <img src="" alt="">
    <script>
        console.log(document.title)
        // let flag=true;
        // setInterval(function(){
        //     if (flag) {
        //         document.title="hello";
        //     } else {
        //         document.title="你好";
        //     }
        //     flag=!flag;
        // },1000)
        console.dir(document.head);
        console.dir(document.body);
        console.dir(document.all);
        console.dir(document.forms);
        console.dir(document.images);
        console.log(document.getElementsByTagName("h1"));
        console.log(document.getElementsByClassName("one"));
        console.log(document.getElementById("a"));
        console.log(document.querySelector(".o"));
        console.log(document.querySelectorAll(".oe"));
    </script>
</body>
</html>